Thermoset binders for composite fiber products such as fiberglass insulation are moving away from traditional formaldehyde-based compositions. Formaldehyde is considered a probable human carcinogen, as well as an irritant and allergen, and its use is increasingly restricted in building products, textiles, upholstery, and other materials. In response, binder compositions have been developed that do not use formaldehyde or decompose to generate formaldehyde.
One type of these formaldehyde-free binder compositions rely on esterification reactions between carboxylic acid groups in polycarboxy polymers and hydroxyl groups in alcohols. Water is the main byproduct of these covalently crosslinked esters, which makes these binders more environmentally benign, as compared to traditional formaldehyde-based binders. However, these formaldehyde-free binder compositions also make extensive use of non-renewable, petroleum-based ingredients. Thus, there is a need for formaldehyde-free binder compositions that rely less on petroleum-based ingredients.
As an abundant and renewable material, protein has great potential to be an alternative to petroleum-based binders. Proteins are already used extensively as a component of adhesives for various substrates. However, many types of protein-containing adhesives have poor gluing strength and water resistance. Thus, there is a need to improve the bonding strength and water resistance of protein-containing binder compositions to levels that are similar to or better than those of conventional, petroleum-based binder compositions. These and other issues are addressed in the present application.